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421 mateuszvis 1
/* This file is part of the SvarCOM project and is published under the terms
2
 * of the MIT license.
3
 *
949 mateusz.vi 4
 * Copyright (C) 2021-2022 Mateusz Viste
421 mateuszvis 5
 *
6
 * Permission is hereby granted, free of charge, to any person obtaining a
7
 * copy of this software and associated documentation files (the "Software"),
8
 * to deal in the Software without restriction, including without limitation
9
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10
 * and/or sell copies of the Software, and to permit persons to whom the
11
 * Software is furnished to do so, subject to the following conditions:
12
 *
13
 * The above copyright notice and this permission notice shall be included in
14
 * all copies or substantial portions of the Software.
15
 *
16
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
22
 * DEALINGS IN THE SOFTWARE.
23
 */
351 mateuszvis 24
 
25
#include <i86.h>
26
#include <string.h>
27
 
367 mateuszvis 28
#include "env.h"
369 mateuszvis 29
#include "helpers.h"
367 mateuszvis 30
 
351 mateuszvis 31
#include "rmodinit.h"
32
 
33
 
449 mateuszvis 34
/* returns far pointer to rmod's settings block on success */
479 mateuszvis 35
struct rmod_props far *rmod_install(unsigned short envsize, unsigned char *rmodcore, unsigned short rmodcore_len) {
351 mateuszvis 36
  char far *myptr, far *mcb;
37
  unsigned short far *owner;
478 mateuszvis 38
  const unsigned short sizeof_rmodandprops_paras = (0x100 + rmodcore_len + sizeof(struct rmod_props) + 15) / 16;
453 mateuszvis 39
  unsigned short rmodseg = 0xffff;
454 mateuszvis 40
  unsigned short envseg, origenvseg;
465 mateuszvis 41
  struct rmod_props far *res;
351 mateuszvis 42
 
453 mateuszvis 43
  /* read my current env segment from PSP and save it */
454 mateuszvis 44
  envseg = *((unsigned short *)0x2c);
45
  origenvseg = envseg;
351 mateuszvis 46
 
369 mateuszvis 47
  /* printf("original (PSP) env buffer at %04X\r\n", envseg); */
449 mateuszvis 48
 
49
  /* if envseg is zero, then enforce our own one (MSDOS 5 does not provide a default env) */
50
  if ((envseg == 0) && (envsize == 0)) envsize = 256;
51
 
351 mateuszvis 52
  /* if custom envsize requested, convert it to number of paragraphs */
53
  if (envsize != 0) {
54
    envsize += 15;
55
    envsize /= 16;
56
  }
57
 
58
  _asm {
59
    /* link in the UMB memory chain for enabling high-memory allocation (and save initial status on stack) */
60
    mov ax, 0x5802  /* GET UMB LINK STATE */
61
    int 0x21
62
    xor ah, ah
63
    push ax         /* save link state on stack */
64
    mov ax, 0x5803  /* SET UMB LINK STATE */
65
    mov bx, 1
66
    int 0x21
67
    /* get current allocation strategy and save it in DX */
68
    mov ax, 0x5800
69
    int 0x21
70
    push ax
71
    pop dx
72
    /* set strategy to 'last fit, try high then low memory' */
73
    mov ax, 0x5801
74
    mov bx, 0x0082
75
    int 0x21
76
    /* ask for a memory block and save the given segment to rmodseg */
77
    mov ah, 0x48
449 mateuszvis 78
    mov bx, sizeof_rmodandprops_paras
351 mateuszvis 79
    int 0x21
80
    jc ALLOC_FAIL
81
    mov rmodseg, ax
82
    /* ask for a memory block for the environment and save it to envseg (only if custom size requested) */
83
    mov bx, envsize
84
    test bx, bx
85
    jz ALLOC_FAIL
86
    mov ah, 0x48
87
    int 0x21
88
    jc ALLOC_FAIL
89
    mov envseg, ax
90
 
91
    ALLOC_FAIL:
92
    /* restore initial allocation strategy */
93
    mov ax, 0x5801
94
    mov bx, dx
95
    int 0x21
96
    /* restore initial UMB memory link state */
97
    mov ax, 0x5803
98
    pop bx       /* pop initial UMB link state from stack */
99
    int 0x21
100
  }
101
 
102
  if (rmodseg == 0xffff) {
369 mateuszvis 103
    outputnl("malloc error");
449 mateuszvis 104
    return(NULL);
351 mateuszvis 105
  }
106
 
1587 mateusz.vi 107
  /* copy my own PSP where RMOD is about to land, so it has a proper PSP as well */
108
  /* take care to init the JFT (20 bytes starting at offset 0x18) to 0xff, which
109
   * essentially means "empty JFT slot" */
351 mateuszvis 110
  myptr = MK_FP(rmodseg, 0);
459 mateuszvis 111
  {
112
    unsigned short i;
113
    char *mypsp = (void *)0;
114
    for (i = 0; i < 0x100; i++) myptr[i] = mypsp[i];
1587 mateusz.vi 115
    for (i = 0x18; i < 0x18+20; i++) myptr[i] = 0xff;
459 mateuszvis 116
  }
1587 mateusz.vi 117
 
118
  /* patch up RMOD's PSP: Parent's PSP segment @ 0x16-0x17 */
119
  myptr[0x16] = rmodseg & 0xff; /* RMOD is his own parent */
120
  myptr[0x17] = rmodseg >> 8;
121
 
122
  /* patch up RMOD's PSP: SS:SP pointer @ 0x2E-0x31 */
123
  myptr[0x2e] = 254; /* I abuse the PSP's command line tail as stack */
124
  myptr[0x2f] = 0;
125
  myptr[0x30] = rmodseg & 0xff;
126
  myptr[0x31] = rmodseg >> 8;
127
 
128
  /* patch up RMOD's PSP: JFT size @ 0x32-0x33 */
1588 mateusz.vi 129
  myptr[0x32] = 20; /* default JFT size (max that fits without an extra allocation) */
1587 mateusz.vi 130
  myptr[0x33] = 0;
131
 
132
  /* patch up RMOD's PSP: JFT pointer @ 0x34-0x37 */
133
  myptr[0x34] = 0x18; /* the JFT is in the PSP itself */
134
  myptr[0x35] = 0;
135
  myptr[0x36] = rmodseg & 0xff;
136
  myptr[0x37] = rmodseg >> 8;
137
 
138
  /* patch up RMOD's PSP: pointer to previous PSP @ 0x38-0x3B */
139
  myptr[0x38] = 0;
140
  myptr[0x39] = 0;
141
  myptr[0x3A] = rmodseg & 0xff;
142
  myptr[0x3B] = rmodseg >> 8;
143
 
144
  /* copy rmod to its destination (right past the PSP I prepared) */
459 mateuszvis 145
  myptr = MK_FP(rmodseg, 0x100);
478 mateuszvis 146
  _fmemcpy(myptr, rmodcore, rmodcore_len);
351 mateuszvis 147
 
1587 mateusz.vi 148
  /* mark rmod memory (MCB) as "self owned" */
351 mateuszvis 149
  mcb = MK_FP(rmodseg - 1, 0);
150
  owner = (void far *)(mcb + 1);
151
  *owner = rmodseg;
152
  _fmemcpy(mcb + 8, "SVARCOM", 8);
153
 
1587 mateusz.vi 154
  /* mark env memory (MCB) as "owned by rmod" */
359 mateuszvis 155
  mcb = MK_FP(envseg - 1, 0);
156
  owner = (void far *)(mcb + 1);
157
  *owner = rmodseg;
158
  _fmemcpy(mcb + 8, "SVARENV", 8);
351 mateuszvis 159
 
449 mateuszvis 160
  /* if env block is newly allocated, fill it with a few NULLs */
161
  if (envsize != 0) {
162
    owner = MK_FP(envseg, 0);
163
    owner[0] = 0;
164
    owner[1] = 0;
165
  }
166
 
537 mateuszvis 167
  /* set CTRL+BREAK handler to rmod */
168
  _asm {
169
    push ax
170
    push dx
171
    push ds
172
    mov ax, 0x2523
173
    mov ds, rmodseg
174
    mov dx, RMOD_OFFSET_BRKHANDLER
175
    int 0x21
176
    pop ds
177
    pop dx
178
    pop ax
179
  }
180
 
983 mateusz.vi 181
  /* mark the input buffer as empty */
182
  myptr = MK_FP(rmodseg, RMOD_OFFSET_INPUTBUF);
987 mateusz.vi 183
  myptr[0] = 128;  /* max acceptable length */
184
  myptr[1] = 0;    /* len of currently stored history string */
185
  myptr[2] = '\r'; /* string terminator */
186
  myptr[3] = 0xCA; /* signature to detect stack overflow damaging the buffer */
187
  myptr[4] = 0xFE; /* 2nd byte of the signature */
983 mateusz.vi 188
 
449 mateuszvis 189
  /* prepare result (rmod props) */
478 mateuszvis 190
  res = MK_FP(rmodseg, 0x100 + rmodcore_len);
450 mateuszvis 191
  _fmemset(res, 0, sizeof(*res));  /* zero out */
192
  res->rmodseg = rmodseg;          /* rmod segment */
453 mateuszvis 193
  res->origenvseg = origenvseg;    /* original environment segment */
449 mateuszvis 194
 
459 mateuszvis 195
  /* write env segment to rmod's PSP */
351 mateuszvis 196
  owner = MK_FP(rmodseg, RMOD_OFFSET_ENVSEG);
197
  *owner = envseg;
198
 
366 mateuszvis 199
  /* write boot drive to rmod bootdrive field */
200
  _asm {
201
    push ax
202
    push bx
203
    push dx
204
    push ds
205
    mov ax, 0x3305 /* DOS 4.0+ - GET BOOT DRIVE */
206
    int 0x21 /* boot drive is in DL now (1=A:, 2=B:, etc) */
207
    add dl, 'A'-1 /* convert to a proper ASCII letter */
208
    /* set DS to rmodseg */
209
    mov ax, rmodseg
210
    mov ds, ax
211
    /* write boot drive to rmod bootdrive field */
212
    mov bx, RMOD_OFFSET_BOOTDRIVE
213
    mov [bx], dl
214
    pop ds
215
    pop dx
216
    pop bx
217
    pop ax
218
  }
219
 
450 mateuszvis 220
  /* save my original parent in rmod's memory */
221
  res->origparent = *((unsigned long *)0x0a); /* original parent seg:off is at 0x0a of my PSP */
222
 
448 mateuszvis 223
  /* set the int22 handler in my PSP to rmod so DOS jumps to rmod after I
224
   * terminate and save the original handler in rmod's memory */
454 mateuszvis 225
  {
226
    unsigned short *ptr = (void *)0x0a; /* int22 handler is at 0x0A of the PSP */
227
    ptr[0] = RMOD_OFFSET_ROUTINE;
228
    ptr[1] = rmodseg;
351 mateuszvis 229
  }
230
 
449 mateuszvis 231
  return(res);
351 mateuszvis 232
}
233
 
234
 
449 mateuszvis 235
/* look up my parent: if it's rmod then return a ptr to its props struct,
975 mateusz.vi 236
 * otherwise return NULL
983 mateusz.vi 237
 * I look at PSP[Ch] to locate RMOD (ie. the "terminate address") */
479 mateuszvis 238
struct rmod_props far *rmod_find(unsigned short rmodcore_len) {
983 mateusz.vi 239
  unsigned short *parent = (void *)0x0C;
448 mateuszvis 240
  unsigned short far *ptr;
241
  const unsigned short sig[] = {0x1983, 0x1985, 0x2017, 0x2019};
465 mateuszvis 242
  unsigned char *cmdtail = (void *)0x80;
448 mateuszvis 243
  unsigned char i;
244
  /* is it rmod? */
459 mateuszvis 245
  ptr = MK_FP(*parent, 0x100);
449 mateuszvis 246
  for (i = 0; i < 4; i++) if (ptr[i] != sig[i]) return(NULL);
465 mateuszvis 247
  /* match successfull (rmod is my parent) - but is it really a respawn?
248
   * command-line tail should contain a single character '\r' */
249
  if ((cmdtail[0] != 1) || (cmdtail[1] != '\n')) return(NULL);
250
  cmdtail[0] = 0;
251
  cmdtail[1] = '\r';
252
  /* */
478 mateuszvis 253
  return(MK_FP(*parent, 0x100 + rmodcore_len));
351 mateuszvis 254
}
367 mateuszvis 255
 
256
 
257
/* update rmod's pointer to comspec */
258
void rmod_updatecomspecptr(unsigned short rmod_seg, unsigned short env_seg) {
259
  unsigned short far *comspecptr = MK_FP(rmod_seg, RMOD_OFFSET_COMSPECPTR);
439 mateuszvis 260
  char far *comspecfp = env_lookup_val(env_seg, "COMSPEC");
367 mateuszvis 261
  if (comspecfp != NULL) {
439 mateuszvis 262
    *comspecptr = FP_OFF(comspecfp);
367 mateuszvis 263
  } else {
264
    *comspecptr = 0;
265
  }
266
}
949 mateusz.vi 267
 
268
 
269
/* allocates bytes of far memory, flags it as belonging to rmod
957 mateusz.vi 270
 * the new block can be optionally flagged as 'ident' (if not null) and zero
271
 * out the newly allocated memory.
949 mateusz.vi 272
 * returns a far ptr to the allocated block, or NULL on error */
957 mateusz.vi 273
void far *rmod_fcalloc(unsigned short bytes, unsigned short rmod_seg, char *ident) {
949 mateusz.vi 274
  unsigned short far *owner;
275
  unsigned short newseg = 0;
276
 
277
  /* ask DOS for a memory block (as high as possible) */
278
  _asm {
279
    push bx /* save initial value in BX so I can restore it later */
280
 
281
    /* get current allocation strategy and save it on stack */
282
    mov ax, 0x5800
283
    int 0x21
284
    push ax
285
 
286
    /* set strategy to 'last fit, try high then low memory' */
287
    mov ax, 0x5801
288
    mov bx, 0x0082
289
    int 0x21
290
 
291
    /* ask for a memory block and save the given segment to rmodseg */
292
    mov ah, 0x48  /* Allocate Memory */
293
    mov bx, bytes
294
    add bx, 15    /* convert bytes to paragraphs */
295
    shr bx, 1     /* bx /= 16 */
296
    shr bx, 1
297
    shr bx, 1
298
    shr bx, 1
299
    int 0x21
300
 
301
    /* error handling */
302
    jc FAIL
303
 
304
    /* save newly allocated segment to newseg */
305
    mov newseg, ax
306
 
307
    FAIL:
308
    /* restore initial allocation strategy */
309
    mov ax, 0x5801
310
    pop bx
311
    int 0x21
312
 
313
    pop bx /* restore BX to its initial value */
314
  }
315
 
316
  if (newseg == 0) return(NULL);
317
 
318
  /* mark memory as "owned by rmod" */
319
  owner = (void far *)(MK_FP(newseg - 1, 1));
320
  *owner = rmod_seg;
321
 
322
  /* set the MCB description to ident, if provided */
323
  if (ident) {
324
    char far *mcbdesc = MK_FP(newseg - 1, 8);
325
    int i;
326
    _fmemset(mcbdesc, 0, 8);
327
    for (i = 0; (i < 8) && (ident[i] != 0); i++) { /* field's length is limited to 8 bytes max */
328
      mcbdesc[i] = ident[i];
329
    }
330
  }
331
 
957 mateusz.vi 332
  /* zero out the memory before handing it out */
333
  _fmemset(MK_FP(newseg, 0), 0, bytes);
334
 
949 mateusz.vi 335
  return(MK_FP(newseg, 0));
336
}
337
 
338
 
957 mateusz.vi 339
/* free memory previously allocated by rmod_fcalloc() */
949 mateusz.vi 340
void rmod_ffree(void far *ptr) {
341
  unsigned short ptrseg;
342
  unsigned short myseg = 0;
343
  unsigned short far *owner;
344
  if (ptr == NULL) return;
345
  ptrseg = FP_SEG(ptr);
346
 
347
  /* get my own segment */
348
  _asm {
349
    mov myseg, cs
350
  }
351
 
352
  /* mark memory in MCB as my own, otherwise DOS might refuse to free it */
353
  owner = MK_FP(ptrseg - 1, 1);
354
  *owner = myseg;
355
 
356
  /* free the memory block */
357
  _asm {
358
    push es
359
    mov ah, 0x49  /* Free Memory Block */
360
    mov es, ptrseg
361
    int 0x21
362
    pop es
363
  }
364
}
963 mateusz.vi 365
 
366
 
367
/* free the entire linked list of bat ctx nodes (and set its rmod ptr to NULL) */
368
void rmod_free_bat_llist(struct rmod_props far *rmod) {
369
  while (rmod->bat != NULL) {
370
    struct batctx far *victim = rmod->bat;
371
    rmod->bat = rmod->bat->parent;
372
    rmod_ffree(victim);
373
  }
374
}